Mount for radiotubes



July 9, 1929. A. B. DU MONT MOUNT FOR RADIO TUBES Filed Aug. 21, 1925 INVENTOR ALLEN B. DONG/VT ATTORNEY Patented July 9, 1929.

UNITED STATES r 1,719,968 PATENT OFFICE.

ALLEN B. DU MONT, 0F MONTCLAIR, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

MOUNT FOR RADIOTUBES.

Application filed August 21, 1925. Serial No. 51,561.-

This invention relates to electron discharge devices such as radio tubes used in audio or radio frequency amplifiers in wireless systems or the like.

An obje'ct of the invention is to simplify the construction of the various elements comprising a mount for radio tubes.

Another object of the invention is to so construct a mount as to facilitate the assembly of the various elements of which the mount is comprised.

A further object of the invention is to provide a radiotron'mount having one element so disposed with relation to the component parts of the mount that the disposition of other elements is facilitated.

A further object of the invention is to pro vide a radiotron mount having the plate'ele-,

ment thereof so disposed with respect to sup porting structure of the mount as to facilitate the disposition of a filament within the gr1d and plate.

A further objept of the invention is to provide a radiotron mount having support members thereof held in positive uniform spaced relation and with a plate mounted upon one of said supports in such position as to facilitate the introduction of other elements within the plate.

A further object of the invention is to provide a radiotron mount so constructed and arranged as to enable an operator to conveniently and expeditiously align one element in given relation to-other component parts of the mount.

A still further object of the invention is to provide a radiotron mount in which the tension applied to a filament or cathode may be quickly ascertained by inspection and conveniently adjusted.

A still further object of the invention is to provide a mountfor a radiotron in which a filament may be conveniently adjusted so as to be tension-ally supported when cold and provided with a slight slack when in operation or heated. 1

Other objects and advantages of the inven tion will be apparent as the description proceeds. y

In radio communication, electron discharge devices known as vacuum or radio tubes are used to receive, amplify or to generate oscillations. Such tubes usually comprise an evacuated envelope having suitably mounted therein a filament or cathode, a grid or control element and an anode or plate.

The above mentioned elements are assembled in a given spaced relation and are secured to support members, which members are generally embedded in what is termed a press or squash at one end of a glass tube termed a flare tube. When the elements, are mounted on supports embedded in the glass of a flared tube, the resultant, structure is termed a mount. The mounts are then sealed to bulbs or envelopes which surround the mounts andwhich are subsequently evacuated either through the tip of the bulb or through an exhaust tube which may constitute a part of the mount when a so-called tipl-ess type of mount is employed.

Radiotron mounts vary in their general construction or mode of assembly; that is, the various elements although fundamentally operating the same are found to give more desirable results and have other meritorious characteristics when given various shapes or configurations in transverse cross section.

The type of radio tube and the structure of the mount thereof employed herein as a selected embodiment of the present invention includes what may be termed cylindrical electrodes. These electrodes consist of a filament wire having a helical wire member disposed therearound to provide a grid and a cylindrical plate positioned around the grid. The filament in this type of tube is relatively long in order that the desired characteristics may be attained and in consequence great difiiculty has been experienced in properly positioning the filament upon the vertical axis of the surrounding elements in order that each tube may have the same characteristics. Furthermore, it has been difficult to properly determine whether or not the filament had the proper degree of tension thereon in order to prevent excessive sagging when heated which would change the characteristics or possibly short circuit the elements. It has heretofore been found inconvenient to determine whether or not the electrodes were properly disposed in uniform relation to give likefresults in all tubes.

The above disadvantages resulted from a construction which had been employed and in which the plate and other elements were located directly above the compressed glass portion of, the flare tube.

-VVhen assci'nblying a mount, the grid and plate must be secured in proper relative positions, after which the filament is passed through the grid until it extends beyond the end of the grid adjacent to the press of the mount and is thensecure-d to a support or lead. 'After being so secured the filament is welded to another support or lead extending over the opposite ends of the grid and plate.

he present invention which provides for the outrigging or olfset arrangement of the cylindrical elements greatly facilitates not only the assembly of the filament within the grid and plate, but the adjustment of the grid within the plate. It will be evident that when the several parts are assembled, an

. operator will have a clear sight through the elements to inspect their relation and properly adjust them, whereas, heretofore this sight was interrupted by the press, making it difficult to determine whether the parts were in alignment."

The invention will be more fully under stood by reference to the accompanying drawing, in which Fig. 1 is a side elevational view of a radio tube broken away showing a mount embodying the present invention;

Fig. 2 is a view similar to Fig. 1 but shows a rear view of the mount;

Fig. 3 is a view taken on line III-III in Fig. 1;

Fig. tis a view taken on line IVIV in Fig. 1; i

Fig. 5 is a view taken on line V-V in 1; and

Fig. 6 is a view showing a mount in position during the assembly of a filament.

Although the present invention may be employed with various electrical devices, it is shown and describe-d herein as employed in connection with a radio tube comprising a sealed container or envelope 10 comprising the usual stem 11 sealed to the tube at 12.

A stem may comprise a flare tube 13 terminating in a so-called press 141 in which leading-in wires or conductors 15, 16, 17 and 18 are embedded and connected in the usual manner to contact pins 19 in a base 20. The tube illustrated includes a plate or anode 21, a grid or control element 22 and a filament or cathode 23. The plate as shown is l'n'eferably of tubular form as is also the grid which is in the form of a helix and positioned concentrically within the plate while the filament is disposed on the longitudinal axis of the said grid and plate.

For the purpose of offsetting the electrodes with respect to the press or axial line of the bulb, the present invention employs a plurality of vertical support wires 2st, 25 and 26.

' These wires have their lower ends embedded in the press 14: and are connected to leads 16, 17 and 18, respectively.

For the purpose of properly spacing the supports and maintaining them in uniform relation in tubes employing relatively long electrodes, as for example in power tubes, a spacer bar 27 of any suitable non-conductive material as lavite is employed. This bar is provided with properly positioned apertures 28 so that the bar may be dropped over the upper ends of the support wires to hold the same in a given relation.

As will be noted from Figs. 3 to 5 of the drawing, the plate 21 may be made of sheet metal bent to tubular form and provided with otfset portions or beaded strips 29 which may be initially spaced apart to embrace the support 24 to which the strips are welded or otherwise secured when the plate is in position.

lVhen assembling the several elements constituting a mount, a suitable rack or handmay be employed and it has been found desirable to first support the grid 22 and plate 21 in fixed relation. A spacer bar 27 is then inserted over the free ends of the supports 25 and 26 which are embedded in the press of the stem 11, prior to the sealing of the stem to the bulb. The stem is then so positioned as to bring the support wire 25 between the strips 29 of the plate and the bent ends 30 and 31 of the support wire 32 of the grid are positioned in contact with and adjacent to the lower and upper ends of the support wire 24, the spacer bar being disposed between the normal upper end of the plate and the bent portion 31 of the support 32, thus limiting the vertical movement of the bar. The plate is then secured by welding the strips 29 to the support 25 and the bent portions of the grid support 32 are welded to the support 24.

It will be understood that the several support wires are rigidly held in a proper spaced relation and a grid and plate mounted firmly thereto. Both the grid and the plate, as will" be. evident from Figs. 3 to 5, are positioned in offset relation to the press portion 14; of the stem, thus making it convenient to inspect and align these elements in proper spaced relation; that is, to bring the longitudinal axes of the elements in coincidence.

By reason of the present construction the introduction of the filament is greatly facilitated; as shown in Fig. 6. the filament 23 may readily be positioned within the grid and plate. An end 33 of the filament is then secured to an adjustable support member M which member is embedded in the press 14 and connected to a leading-in wire 15. This support member is constructed so as to have a relatively long arm and may be made of comparatively large diameter but of soft or malleable material so as to be easily bent to various positions.

When a filament has been secured to the support 34 by welding jaws 35, indicated in dotted lines, the opposite end of the filament is disposed upon a resilient tension member 36 which is secured adjacent to the normal upper end of the support 26.

As illustrated in Fig. 6, the filament may be stretched prior to the second welding operation, which. stretching is. performed by gripping an end 37 of the filament between a pair of gripping jaws 38. The jaws are attached to one end of a cable 39 passing over a pulley 41 and having a. weight 42 attached to the opposite end. When properly stretched, welding jaws 34 indicated in dotted lines in Fig. 6 may be operated to secure the filament 36 after which the excess portion of the filment may be severed.

The method of i'nounting the filament as above described is more clearly shown in copending application, Serial No. 694,552, filed February 23, 1924, and assigned to the same assignee as is the present invention.

In the mounting of filaments as employed in the type of tube illustrated, each end of the filament is provided with a relatively heavy section of wire, which sections are more readily Welded to the supports than would be the fine filament wire. v

One method of mounting the filament is given above but it will be understood that other methods may be used for which the present construction is equally advantageous.

It will benoted that the supportjmember 34 is bent to provide a relatively long lever arm to which the normal lower end of the filament is secured. The upper end of the filament is secured to a member 36 of greater flexibility. j

The present invention is particularly advantageous by reason of the efact that as above set forth, the elements are" offset with respect to the plate, allowing for the unobstructed sight on the part of the operator to properly adjust the elements after they have been secured in position in the event that they are out of alignment.

By reason of the flexibility of the upper filament support 36 and the adjustability or pliability of the lower filament support 34, it is possible for the operator to adjust the lower support to effect a slight longitudinal tension upon the filament. creatinga slight internal tension in the filmcnt support 36.

This may be accomplished by an operator after a filament is mounted by bending the free end of the support 34 downwardly, the said lower support remaining in position as adjusted by reason of itscomparatively low fiexibilty with respect to the support 36. When a filament is so adjusted, it is held taut when cold and thus prevented'from breaking by reason of shocks or jars during transportation or other handling. Then in operation,

however, the filament becomes heated and slightly extended, causing the filament support to at least partially return to its normal of mierophon'ic effects as exist under ordinary conditions when a filament is heldiinder appreciable tension during operation. urthermore when a filament is mounted in the present construction, the same may be readily tested as to whether the filament is in the desired taut condition and this is accomplished by slightly bending the support 34 and observing the pull upon the upper support 36.

Although, as above stated, the present invcntion applicable to various types of tubes, it .is especially desirable in the type shown wherein a fine filament is located concentrically within. either one or a plurality of tubular electrodes, since the free passage through the electrodes facilitates the tensioning and inserting operations.

By reason of the clearance provided for the passage of the filament, the present construction lends'itself to rapid operations, such as may be performed by hand or by automatic means. It will be further noted that although the plate is shown as secured to the central member 25, it may be secured at one side as for example on the support 26, while the tension member 36 which carried the filament may be secured to the central support.

By reason of the present invention, considerable time and effort is saved in the manufacture of radiotron mounts and the cost ofsuch operations is greatly reduced.

Although a preferred embodiment of the invention is shown and described herein, it is to be understood that modifications may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

lVhat is claimed is:

l. A mount for an electrical device comprising a stem having a symmetrically positioned press, a support member embedded in said press, a tubular electrode mounted on said support. said electrode being offset so that the perimeter of the tubular portion thereof is disposed at one side of and without the boundary of said press.

2. A mount for an electrical device comprising a stem having a symmetrically positioned press, a leading-in support wire embedded in said press, a tubular member having an offset portion associated with said support member to position said tubular member on a line external of said press and with the perimeter of the tubular member at one side of said press so as to provide an unobstructed passage through said member.

3'. A mount for an electrical device comprising a stem having a press, a plurality of support members embedded in said press in spaced relation, a spacer member applicable to the free ends of said support members to hold the same in given spaced relation and a plurality of tubular electrodes secured to said supports, all of said electrodes having the perimeters of their tubular portions positioned outside the boundary of said press to provide an unobstructed passage through said tubular electrodes. l. An evacuated vessel containing a press, a support Wire secured in the press, a tubular electrode associated with said support Wire and offset with respect to the boundary of said press to provide an unobstructed passage through said tubular electrode.

5. An ovacautcd vessel containing a press, a plurality of support wires embedded in said press, a tubular electrode secured to one of said support Wires and a cathode disposed within said tubular electrode, said tubular in said tubular electrode and flexible support members embedded in said press and secured to opposite 'ends of the cathode, said support members being movable to adjust the position of said cathode.

In testimony whereof, I have hereunto subscribed my name this 20th day of August,

ALLEN B. DU MONT. 

